Apparatus and method for metal casting



July 27, 1965 A. 'r. BALEVSKY ETAL 3,195,501

APPARATUS AND METHOD FOR METAL CASTING Filed Feb. 13. 1962 FIG.3

IN VEN TORS. ANGEL TONT$CIIE V BALE VSK Y IVAN DIMOV N/KOL 0V A T TORMEYS.

United States Patent 3,196,501 APPARATUS AND METHOD FGR METAL CASTING Angel T. Balevsky and Ivan D. Nikolov, Sofia, Bulgaria, assignors to Balgarsira Akademia Na Naukite, Sofia, Bulgaria Filed Feb. 13, 1962, Ser. No. 173,052 Claims. (Cl. 2268) This invention relate in general to metal casting apparatus and to a method of casting; and, in particular, to an improved apparatus and method for casting materials using counter-pressure.

The present invention refers particularly to pressure casting. At the present time it is usual when casting under pressure to direct the molten metal into a pressmold or pressure mold in the form of a jet under pressure exerted by a pressure producing means such as a movable piston or a compressed air reserve tank. A disadvantage of such method is that intense whirling of the molten metal With the air or gases in the pressmold takes place and this results in the entrapment of the air or gases in the molten mass making the resultant cast pieces porous. With such prior art methods, the pressmold is subjected to atmos-" pheric pressure and the casting can be subjected to high pressure only after the mold is filled up at which time the air in the mold already mixes with the molten metal and the solidifying of the metal in some portions of the casting has already begun. This results in disadvantageous blowholes in the casting due to the bubbles of air or gases which become entrapped in the casting. When attempts are made to exert extremely high pressures on the casting in order to reduce the size of such bubbles and to obtain I a more precise casting, the apparatus becomes unusually expensive or the dimensions and weight limits of the casting are unduly restricted.

' In accordance with the present invention the casting is formed by subjecting the mold to a pressure which advantageously may be regulated to desired amounts above atmosphere and by imposing a larger pressure on the molten metal which is injected into the mold. With such a method and apparatus to effect the same, the disadvantages mentioned above are eliminated. The improved method and apparatus are effected by controlling the pressure within the mold as well as the pressure of the molten metal being injected thereinto. In this manner it is possible to regulate the speed at which the molten metal rises in the pressmold in a way so that neither breaking of the free surface nor mixing of the molten metal With air or gases results. In addition, in accordance with this method it i also possible to maintain the pressmold and the molten metal therein under the continuous action of a preliminary predetermined pressure insuring in this manher the production of an exact impression.

In accordance with one embodiment of the apparatus A a pressmold is arranged between a pressure compensating fluid source is also communicated with the molten metal reservoir.

When the apparatus is rotated, the molten metal reservoir i disposed above the mold so that the molten metal flows down under the gravity head of the 3,196,591 Patented July 27, 1965 height of molten metal in the reservoir above the mold. Additional pressure regulation is achieved by the compressed air reservoir to regulate the pressure acting downwardly on the molten liquid to force it into the mold and to regulate the pressure acting on the top of the mold upon the surface of the liquid as it is being moved upwardly into the mold.

In still another embodiment of the invention there is provided a reservoir of molten liquid which communicates directly with the pressure mold at the lower end thereof and valve means for regulating the pressure at the upper end of the mold. A piston is arranged to act upon the liquid in the molten liquid reservoir to force it into the pressure mold against the pressure which acts on the upper end thereof.

Accordingly, it is an object of this invention to provide an improved method for casting metals under pressure.

A further object of the invention is to provide an apparatus for casting metals under pressure.

A further object of the invention is to provide a method of casting metals under pressure which includes pressurizing one side of a mold and directing molten metal into the opposite side of the mold by a greater pressure regulated to permit uniform rising in the mold without turbulence or entrapment of fluid in the molten metal.

A further object of the invention is to provide an improved device for casting metals under pressure which includes a pressure mold which is connected to a reservoir for feeding molten liquids thereinto at one end and is subjected to a pressure above atmospheric at its opposite end and means for regulating the pressure to permit the rising of the metal into the mold while maintaining the metal at a pressure above atmosphere.

A further object of the invention is to provide a method and apparatus for casting under pressure which is simple in concept, economical to carry out and provides a casting of improved characteristics.

The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this specification. For a better understanding of the invention, its operating advantages and specific objects attained by its use, reference should be had to the accompanying drawings and descriptive matter in which there are illustrated and described preferred embodiments of the invention.

In the drawings:

FIG. 1 is a diagrammatic illustration of an apparatus for casting metals under pressure constructed in accordance with the invention;

FIG. 2a is a diagrammatic illustration of another embodiment of the apparatus for casting metals under pressure;

FIG. 2b is a diagrammatic illustration of the apparatus indicated in FIG. 2a but with the parts oriented in an operating position; and

FIG. 3 is a diagrammatic illustration of still another embodiment of the invention.

Referring to the drawings in particular, as indicated in FIG. 1 the invention includes a pressure mold or pressmold 3 which is provided with a gas permeable outlet 4 at one side and which is provided with a connection to a runner or filler tube 2 at the opposite side. Molten metal is maintained in a feeding reservoir 1 in direct communication with the lower end of the runner tube 2. The gas permeable outlet 4 is sovered by a housing to form a pressure compensating chamber 5.

In accordance with the invention, pressure acting on the mold designated P is regulated to an amount advantageously above atmosphere by directing compressed fluid from a compressed fluid reservoir R through con duits 10 and 12 to the pressure compensating chamber 5.

A further control on this pressure is obtained by regulat ing a discharge valve in aconduit 14.

Initially the pressure P acting on the press mold 3 and a the pressure P in the feed reservoir 1 are equal." -For,

example, this pressure ca'nbe l; 5, 10, 20 etc. atmospheres,

according to the requirements of the particular case. This pressure may be produced, forvexample, by introduction ofa compressed gas, suc h as air, from the fluid reservoir R. Such materialsi as aluminum alloys, 'zinc' alloys, iron,

or the like, may be cast in the apparatus indicated in the drawings. The temperatures and pressuresyrequired will be a functionof the type of metalvor alloy whichlis to be 36. In theembodiment, thepressure mold 36 can be gradually filled with molten nietalunder the control of pr essure created by the force of the piston 44 and the pressure which exists at the top ot the mold 36.

Whilea specific embodiment of the invention has been shown and described in detail to illustrate the application of the inventive principles, it will be understood that the invention may be embodied otherwise without departing cast, the form and size of the press mold 3, and the rate of vcooling. Those skilled in the artjwill' readily be able.

to determine the particulartemperatures and pressures 7 required. H I Whenitis desired todirectthe metal from the feeding reservoir 1 into the pressure'rnold"3,-compressed fluid is; directed fromthe'conduit 10 through a conduit 16'1by open- 1 ing valves d and bin conduits tfl 'and16, respectively Valve a in co'nduitlZ and valve bin conduit 14 are regulated along with valves d andfb to insure that the pressure P is above; atmosphere, but that the pressure P acting downwardly on the molten metal to 'causejiit to feed through the runner" tube 2 is greater than the pressure P acting on the top surface of the metal as it rises in the pressure mold ,3. Thus,. it 'possiblelwith the arrange:

ment .outlinedfto accurately control thespeed at which from such principles. 7

'What is claimed is;

V 1; A- pressure casting device, comprisingrin combination, a mold, a liquefied material reservoir connected to said mold, means for applying the same super' atmospheric pressure tolboth said mold and said liquefied material reservoir, means for establishing apressuredifferential" between said reservoirand'said mold, while 1 maintaining'the pressures at saidreservoir and said mold atv super atmospheric values with the pressure at the mold being lessthan the'pressure'ati'the liquefied material res ervoir, :to'; cause the liquefied material to flow from the reservoir to mold to fill the' mold gradually, and means for maintaining said "pressure differential constant during the entireprocess offillingthemold.

themolten metal will enterinto the pressuremold 3 as determined by the difierentialin pressure between P and P It is possible in accordance with the invention to choose the pressuredifierential so thatthe molten metal remains unbroken as it feeds into the mold 3 and'insure';

that air and other gases existing in the pressure mold'will not form, as bubbles within the metal which is being cast. By maintaining the metal which is being cast under theinfiuence of the pressure P 'during the casting operation,

it is further insured that the exact reproduction of the shape of the, mold will be producedin'the casting. v

' In FIG. 2, a modifiedapparatus isindicatedwhich comprises a rotatablestructure including'a sphericalmolten metal reservoir 20', a pressure m0ld221which communi cates with'the molten metalreservoirthrough anopening 24, and a fluid, pressure reservoir 26, which communicates with the molten metal reservoir through conduits '28- and 30, and with the pressure mold 22 through the conduits 28 and 32. Intheposition' indicated inFIG.2a, the ap- .2. 'pressu re casting device,- as claimed in claim 1, wherein said mold has an; air permeable outlet on one side, said means for applying super atmospheric pressure and 'for maintaining a constant pressure differential compris- "5'. A pressure casting device'jaccording to" claim 1,

including a piston acting on'said-liquefied materialto pressurize the material to cause 'it to flow into said mold.

6. Ina method of casting liquefiedmaterial'by feeding the liquefied material from a' reservoir-thereof to a mold:

the improvement comprisingin advanceof feeding metal to'the mold subjecting the reservoir" and the mold to the same super atmospheric pressure; then establishing apresparatus is shown prior to thedirecting' ofthe molten metal 7 7 into the pressure mold' 22.

In FIG. 2b the apparatus is shown rotated to aposi-- tion in which the molten metalreservoir e20 ,is disposed above the, pressmold 22 so that there'willbe atendency V for the weight of the molten met'al to cause'lflow downwardly through the opening 24 into the =pressmold 22 The pressmold 22 includes an 'elongated narrow'passage 22a extending downwardly from the 'opening 24 anda widened portion ZZb W hiCh communicates through a gas permeable outlet 34 to conduit The pressure IP in themolten metal reservoir z tl'is regulated by directing fluid from the fluid pressure source 26' through vconduit '28 and valve a to the conduit 30 leading to the reservoir sure difierential between the reservoir and-the mold, while maintaining'the pressures in both the reservoir and the mold at a super atmospheric value .with the pressure in the mold being less than that'ingthe reservoir, whereby to cause :the liquefied materialto flow from the reservoir into themoldiandiigradually to: fill the mold; and maintaming-such pressure ditferential constant during' the en tire mold filling process. .ir

casting liquefied material as claimed in claim '6, the improvement comprising controlling the speed atwhichthe liquefiedmaterial' enters the mold by adjusting the pressure differential between the reservoir and the mold. v J a 8. 'In a method otcasting liquefied'material, as claimed in claim'fi, the'improvementwhereinthe pressure in the 20. In additiomathe prssure'acting' atfP in' the chamber,

22b. of the pressure mold 22 is 'co ntrolled' by directing pressure from the fluid Pressure sour'c'efz fi through conf duit28 and conduit32 as regulatedby valves 11,11; and c, 1

In the embodiment indicated in FIG. 3," a :pressmold 36 is provided with an openingSS at itslowfe r end which:

communicates through a tube 40 w ith' 'a'reservoirf42 of molten metal: The molten metal is directed into thelower end of the pressure mold 36 by means of "a piston 44 by maintainingirthe pressures atsaid reservoir and said mold theapplication of aidownward force P indicated by the arrow. The pressure at the top'of the mold is controlled by a valve 46 in a conduit. 48 which, communicates through a' fluid permeable outlet 50 to the top of the, mold reservoir is produced bymeans of adirect'acting piston,

'while the pressure in the mold. is produced by a compressedggas;

,9. Azipr'essure casting device comprising, in ,combi'na- 7 some mold, a liquefiedumaterial reservoir connected to said mold, meari slf orflapplying thetsame super atmospheri'c pressure to both saidmold'and saideliqu efied materialireservoir, means for establishing ai pressure differential between jsaidfreser-voir; andfsaid' mold while fat super atmospheric values withth e' pressure atfthe mold being lessfthan the pressure "attheglliquefied materialreservoir, to cause the iliquefiednmaterialtoflow tromthe said outlet;

reservoir to mold to fill the mold gradually, and means for maintaining said pressure differential constant during the entire process of filling the mold, said liquefied material being maintained in a closed vessel communicating with said mold, said vessel and said mold being rotatable to position said vessel above said mold to permit the flow of the material into the mold under the influence of the Weight of the material above said mold.

10. A pressure casting device comprising, in combination, a mold, a liqufied material reservoir connected to said mold, means for applying the same superatmospheric pressure to both said mold and said liquefied material reservoir, means for establishing a pressure dilferential between said reservoir and said mold, while maintaining the pressure at said reservoir and said mold at superatmospheric values with the pressure at the mold being less than the pressure at the liquefied material reservoir, to cause the liquefied material to flow from the liquefied material reservoir to mold to fill the mold gradually, and means for maintaining said pressure dilferential constant during the entire process of filling the mold, including a reservoir of fluid under pressure connected to one side of said mold and to said liquefied material reservoir.

References Cited by the Examiner UNITED STATES PATENTS 2,210,544 8/40 Galloway 2269 2,310,766 2/43 Dornauf 22209 2,821,757 2/58 Wood 22--69 2,994,115 8/ 61 Schuchardt 2268 2,997,756 8/ 61 Strorn 2269 3,03 2,841 5/62 Sylvester 2269 FOREIGN PATENTS 11,423 7/09 Great Britain.

J. SPENCER OVERHOLSER, Primary Examiner.

WINSTON A. DOUGLAS, MARCUS U. LYONS,

MICHAEL V. BRINDISI, Examiners. 

10. A PRESSURE CASTING DEVICE COMPRISING, IN COMBINATION, A MOLD, A LIQUFIED MATERIAL RESERVOIR CONNECTED TO SAID MOLD, MEANS FOR APPLYING THE SAME SUPERATMOSPHERIC PRESSURE TO BOTH SAID MOLD AND SAID LIQUEFIED MATERIAL RESERVOIR, MEANS FOR ESTABLISHING A PRESSURE DIFFERENTIAL BETWEEN SAID RESERVOIR AND SAID MOLD, WHILE MAINTAINING THE PRESSURE AT SAID RESERVOIR AND SAID MOLD AT SUPERATMOSPHERIC VALUES WITH THE PRESSURE AT THE MOLD BEING LESS THAN THE PRESSURE AT THE LIQUEFIED MATERIAL RESERVOIR, TO CAUSE THE LIQUEFIED MATERIAL TO FLOW FROM THE LIQUEFIED MATERIAL RESERVOIR TO MOLD TO FILL THE MOLD GRADUALLY, AND AND MEANS FOR MAINTAINING SAID PRESSURE DIFFERENTIAL CONSTANT DURING THE ENTIRE PROCESS OF FILLING THE MOLD, INCLUDING A RESERVOIR OF FLUID UNDER PRESSURE CONNECTED TO ONE SIDE OF SAID MOLD AND TO SAID LIQUEFIED MATERIAL RESERVOIR. 